Electric defrosting arrangement for refrigerators



L. w. ATcHlsoN 2,645,905

ELECTRIC DEFROSTING ARRANGEMENT FOR REFRIGERATORS July 21, 1953 Filed Nov. 15, 1950 2 `Sheets-Sheet 2 Inventor Leonard W. Atch son,

Hs Attorneg.

Vheating element.

Patented July 2l, 1953 ELECTRIC DFROSTING ARRANGEMENT FOR REFRIGERA'IKORS Leonard W. Atchison, Erie, Pa., assignor to General Electric Company, a corporation of New York Application November 15, 195,0, SerialNo. 195,858

^ My invention relates to refrigerators and more particularly to arrangements for defrosting reirigerant evaporators or cooling units.

lt'has previously been known to use electric heating for defrosting refrigerator evaporators. Also various means have been provided for automatically initiating the defrost period, for example, initiation in response to a predetermined number of door openings, number of unit cycles, etc. In my improved arrangement, however, provision is made for scanning or sweeping the evaporator with movable' heating elementsv and also provision is made for storing energy for effecting such scanning period.

Accordingly, it is an object of my invention to provide an Vimproved arrangement for' autornaticallyA defrosting refrigerator cooling units or evaporators.

It is another object of my invention to provide an improved arrangement including movable Velectric heating elements for periodically derosting a refrigerator evaporator.

It is a further object of my invention to provide animproved arrangement for rapidly defrosting a refrigerator evaporator.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the clai-ms annexed to and forming a part of this specification.

In carrying out the objects of my invention, an electric heating element is disposed` in a position spaced slightly from and parallel to the wal-ls of a refrigerator evaporator. rI'he heating element is movabiy mounted and mechanism is provided for reciprocating-the heating element parallel to the refrigerator evaporator so as to scan the walls of the evaporator and thereby melt the frost from `all portionsv ofY the walls. A rotatable element is provided forengaging the heating element structure to impart reciprocatf s claims. (C1, A6.241)

defrosting structure; Fig. 4 is a sectional view illustrating details of the mechanism employed for moving and energizing the heating element; Fig. 5 is a view taken along the line 5 5 of Fig. 4; Fig. 6 is a front elevation view showing a modified form of my invention; and Fig. '7 is a side elevation view of the modied form shown in Fig. 6.

ing movement thereto. The mechanism for obtaining such movement includes a spring which is adapted to bev/found to store energy for moving the heating element and it further includes a switch mechanism actuated for energizing the For a vbetter understanding of my invention, reference may be had to the accompanying drawings in which Fig. 1 is a view ofua portion of` a refrigerator incorporating an embodiment of my invention; Eig. 2 is an enlargedsectional side elevation View of thev refrigeratorshown in Fig. 1; Fig.A 3. is. an; enlarged front elevation view of the Referring to Figs. l and. 2, there is shown a refrigerator cabinet l including an outer wall 2 and a spaced inner Wall or liner 3. The space between t-he linner and outer walls is lledwth a. suitable heat-insulating material 4, and the space between. these Walls adjacent the access opening of the refrigerator is closed by a breaker strip 5 of suitable heat-insulating material, such as any of a number of` conventional plastic materials. The liner 3 deiines a food storage compartment 6.,. and the4 access opening of this compartment is closed. by a door 1.

In order to lcool the food storage compartment 6 an evaporator as cooling unit 8 is mounted at the top portion of the compartment 6. The evaporator 8v illustrated is of the type which extends substantiallyk the full width of the `compartment 6.. A door 8 is hinged at lilL for closing the access opening of the evaporator, a handle ll being. provided. for the door 9The evaporator 8. is formed of metalin a generally U-shape having two-side Walls i2 anda bottom. wall. I3 formed from a continuous strip of metal.. The evaporator` is supported from vthe top of the linerk 3: by'screwsill, insulating .blocks y,

'cludes a heating. element I1, Thehea-ting element is made in serpentine form and is bent into a generally -U-shape conforming'to the walls of. the evaporator 8. The yheating element may be of the sheathed conductorA type, comprising,l

for example, a. central electricalconducting wire,

an outer metallic sheath, and an intermediate `insulating powder.

The U-shaped. yheating element structure is spaced slightly from the walls of the evaporator 8 and this structure extends parallel to the walls of the evaporator.

The heat radiating surface of the heating element is relatively smaller than the surface of the evaporator 8 and in order to insure the melting of frost from the entire outer surface of the evaporator 8, the heating element l1 is arranged for reciprocating movement relative to the evaporator so that this heating element in effect scans the entire outer surface of the evaporator. To provide for such reciprocating movement two tracks I8 are secured to the side walls I9 of the liner 3, these tracks extending horizontally from front to rear along the. side walls. The heating element structure includes a plurality of rollers which ride along the tracks I8. These rollers are supported'from the heating element itself by brackets 2l which are secured to the heating element l1 and byfv flanged plates 22 which are secured to the brackets 2l and provide a mounting for the rollers 20. It can be seen that the mounting structure described allows movement of yheating element I1 from front to rear of the refrigerator cabinet, the heating element moving parallel to the walls of the evaporator 6 and being slightly spaced therefrom, for example, by a distance Of ig".

In order to effect reciprocation of the heating element i1 a rotatable disk 23 is provided. This disk 23 is connected by a link 24 with the heating element structure. One end of the link 24 projects through an opening 25 in the disk 23 and the other end of the link 24 is connected to a bracket 26 which is secured to a bar 21. cured to the heating element l1 substantially at the central area of the bottom portion thereof.

Mechanism 23 for rotating the disk 23 is supported on a transversely extending hollow structure 23. This structure 29 extends the full width of the storage compartment, is supported from the evaporator 3, and is further secured to the side walls of the liner 3. The mechanism employed is shown in detail in Figs. 4 and 5. This mechanism 23 includes a housing 30 having .an opening 3l therein for receiving a shaft 32 to which the disk 23 is secured. The mechanism further includes a ratchet wheel 33 rotatably mounted on a shaft 34 which is also supported by the housing 30. The ratchet wheel 33 is actuated by a reciprocating plunger 35 having a pawl 36 secured thereto for engaging the teeth 31 of the ratchet wheel 33. The plunger 35 may be actuated in any desired manner. For purposes of illustration it has been shown projecting through the front face 38 of the structure 29 so that it is engaged by the door 1 each time the door is moved to the closed position. When the door is opened, the plunger is moved outwardly by a resilient leaf element 39 which is secured to the housing 30 by rivets 40 or other suitable securing devices. A stop 4I is secured to the housing by a screw 42 and engages the teeth 31 to prevent reverse movement of the ratchet wheel 33 as the pawl 36 is retracted during the outward movement of plunger 35. By this arrangement the ratchet wheel 33 is advanced one tooth each time the refrigerator door is opened and closed.

A spring 43 is employed for storing energy resulting from the movement of the ratchet wheel 33. The spring 43 is in the form of a spirally wound fiat leaf member, one end of which is connected to the shaft 32 by a screw 44 or other suitable fastening device and the other end of which is secured to a knob or pin 45 which in turn is The bar 21 is sev riveted to the ratchet wheel 33. Thus, assuming that the disk 23 and the shaft 32 are held from rotation as will be described below, movement of the ratchet wheel 33 is effective to wind the spring 43, storing energy which is ultimately available for rotating the disk 23. The mechanism 28 is further constructed to provide for actuation of a switch to energize the electric heating element I1. This latter portion of the mechanism includes an arm 46 pivotally mounted on a pin 41 which is secured to the housing 30. The arm 46 is biased by a spring 48 in an upward direction so that a portion 49 of the arm bears against the lower end 50 of thehubv of the ratchet wheel 33. The free end of the arm 46 is provided with `a knife edge 5I which engages one side of an overcenter hairpin spring 52. A movable switch arm 53 includes a knife edge 54 which engages the opposite side of lthe hairpin spring 52. The switch arm 53 includes a movable contact 55 at the opposite end thereof, the contact 55 being adapted to engage a stationary contact 56 for completing the circuit energizing the heating element I1. Two terminals 51, 53 are provided on the housing 33, the terminal 51 including the stationary contact 56 and the terminal 58 being connected by a wire 53 to the movable switch arm 53. A removable cap 60 is provided for covering the outer ends of the terminals 51, 53 to which the power supply leads are connected. Because of the overcenter hairpin spring 52 the switch arm 53 is adapted to snap from the open to the closed position of the contacts 55, 56, and the upper and lower stops 6I, 62 respectively are mounted on the housing for limiting the movement of the switch arm 53 in each direction.

It can be seen that the switch mechanism is biased to the open position by the spring 43. In order to effect movement of the switch to its closed position the shaft 32 is formed on its lower end with a. cam surface 63 and the upper end of the hub of the ratchet wheel 33 is formed with a cooperating cam surface 64. Assuming again that the disk 23 and its shaft 32 are held against rotation, the movement of the ratchet wheel 33 by the reciprocation of the plunger 35 gradually effects a downward movement of the ratchet wheel 33 because of the cooperation of the cam surfaces 63 and 64. The ratchet wheel 33 is arranged foi sliding movement relative to the shaft 34 on which it is mounted. As the ratchet wheel 33 moves downwardly, the surface 50 of the hub of this wheel moves the engaging portion 43 of the ,arm 46 downwardly and ultimately shifts the arm 46 in a counterclockwise direction by an amount which is sufficient to snap the hairpin spring 52 over center. When this occurs, the hairpin spring effects a simultaneous upward movement of the left-hand end of the switch arm 53 causing the right-hand end of this switch arm to move downwardly and bring the contact 55 into engagement with the contact 56, completing the circuit of the heating element I1.

The operation of the defrosting arrangement is Vas follows. During normal operation of the refrigerating apparatus, frost gradually builds up on the exterior of the walls -of the evaporator 3 and reaches a thickness where it blocks movement of the heating element l1 relative to the evaporator. When movement of the heating element l1 is so blocked, the disk 23 is unable to roltate. Accordingly, subsequent actuations of the plunger 35 as a result of door openings are effective to rotate the ratchet wheel 33 and to wind the spring 43. At the same time, since the shaft 3'2 is had statienary,the're1auve movement'of the ratchet wheel 33 effects, through the cooper rating cam surfaces 63 and 64, a downwardmovement of the ratchet wheel 33. Ultimately this downward movement causes the switch to snap to its closed position energizing the heating element l1. The energization of the heating element l1 effects a melting of the frost in the region adjacent the position ofthe heating element at the -to the evaporator, the limits of its travel being indicated by the solid line and dotted line positions shown in Fig. 2.- The heating element Il moves a'e'liaeos to the liner 3,and includes the plunger 35 which projects` through the front face of the cabinet and is actuated by the door, and the shaft 32 which projects through an opening in the side wallof the` liner 3. The disk "23 is mounted on the shaft 32 within the storage compartment. In orderv to translate rotary motion of .the disk 23'into reciprocating motion of the heating elef ment I1, a rod I68 is pivotally mounted at the top ofthe evaporator 8.` Two downwardlyextending arms 69 and 10 are secured to the rod B8, one at each end of the rod. The arm 69 has a slot 'H formed therein, and a pin 12 mounted on the disk 23v is arranged to project into the'slot 1|. When the `disk 23 is rotated inthe manner described above, the corresponding rotation ofthe pin 12 effects movement of the arm v69 between the solid and the dotted line positions shown in Fig. 7. Since both the arms 69 and 10 are nxed to the pivoted or rotatable shaft 68, movement of the arm 69 effects a simultaneous movement in the manner described until the spring '43" has completely unwound. In the unwinding process; it will be noted that the reverse action takes place with respect to the cam surfaces 63 `and 64 and the ratchet wheel 33 moves upwardly, being biased in this direction by the spring 48 which bears against the arm 4G, the arm 46 inturn bearing against the surface 5l! of the hub ofthe ratchet wheel 33. Ultimately thearrn '46 moves to the overcenter position illustrated in Fig/1, causing the switch arm 53 to snap vthe switch to its open position, de-energizing the heating element l1. This completes the deirosting operation.

In order to dispose of the water resulting from the defrosting of the evaporatonfa sloping bafe plate `65 is provided beneath .the evaporator. Water falling on the baiile plate ;65 is directed toward the rear of the compartment S whereit :lows into a draintrough 56 mounted on the rear wall of. the liner 3. Water from the drain trough may be disposed of in any 'desired manner, for example, by .a tube connected to the trough and extending into the machinery compartment or by merely allowing the water to ilow from the trough down the wall of the liner and ultimatelythrough a drain` opening in the 'bottom of the liner. The structure 29 is provided with a downwardly sloping plate Gl at the rear portion thereof for coll lecting defrost water falling from., the forward portion of the evaporator and ydirecting it onto the baiile plate 35. i

In Figs. 6 and 7 there is of my invention which 4differs from that just described primarily in the specific arrangement for effecting movement of the heating element and in the particular location of the mechanism for enecting this movement. The same numerals have been used to-designate corresponding parts in Figs. 6 and 7 and in Figs. l through 5 inclusive. Referring now to Figs. 6 and 7the evapo-v rator 8 is mounted in the manner previously described at the top portion of the food storage compartment. The heating element |71 is mounted adjacent and parallel to lthe walls" l2 and I3 shown ya modified form.

of the evaporator il, and this heating element is supported for reciprocating movement by rollers 20 on tracks I8. The mechanism 28 for supplying the force for moving the heating element I'I and also for energizing the heating element is disposed within the insulation'space between the inner and outer walls of the refrigerator. This mechanism 28 is secured in any suitable manner of the-arm 10. and l'Nl are received within slots formed in the iiange portion 'I3 of the plates 22, one'such slot being indicated at 14. Thus movement of the arms 69 and 10 between the solid and dotted line positions shown also eifects movement vofthe heating element I1 between the solid `and the dotted line positions. This causes a melting and removal of frost from the evaporator in the same manner that described in previously discussing the form of invention `illustrated in `Figs. 1

through 5.

While I have shown and described specific embodiments of my invention, I do not desire my invention to be limited to the particular construction shown and described and I intend, by the appended claims, to cover all modifications with'-` in the spirit and scopel of my invention.' i

What I claim as new and desire to secure by Letters Patent of the United States is:

l. In a refrigerator including a cooling upon which frost collectsya heating element spaced from the wall of saidk cooling unit, the

rheat radiating surface of saidrheating element being relatively smaller than said wall, said element being movably mounted for movement parallel tojsaid wall,l mechanism effective when op# l erated for rreciprocating.; said heating element parallel to said wall for melting frost therefrom, and means for periodically operating said mechanism and energizing said heating element.

y2. In a refrigeratorv including a cooling unit upon which frost Icollects, 'a` heating element spaced from the wall of said cooling unit, the heat radiating surface of said heating element being relatively Vsmaller than said wall, said element being movably mounted for movement parallel to said Wall, and mechanism for reciprocating said heating element parallel to said wall for melting frost therefrom, saidY mechanism including a roytatable disk and a link engaging said disk vnear the outerxperiphery thereof and connected to said `heating lelement whereby rotation lof said disk is effectiveto reciprocate said heating elee ment. i i i 3. In a refrigerator including a cooling unit upon vwhich frost collects, a heating element spaced from the wall'of said 'cooling unit, the heat radiating' surface of said heating element .being relatively smaller than said wall, said element being movably mounted for movement parallel to saidwall, and mechanism for reciprocaty The lower vends of the arms 69 unit f cluding a rotatable disk and shaft therefor, a link engaging said disk near the louter periphery thereof and connected to said heating element for translating rotary movement of said' disk into reciprocating movement of said heating element, a spring connected to said shaft, and means for winding said spring for storing energy to rotate said disk.

4. In a refrigerator including a cooling unit upon which frost collects, a heating element spaced from the wall of said cooling unit, the heat radiating surface of said heating element being relatively smaller than said wall, said element being movably mounted for movement parallel to said wall, and mechanism for reciprocating said heating element parallel to said wall for melting frost therefrom, said mechanism including a rotatable disk and a shaft therefor, a link engaging said disk near its outer periphery and connected to said heating element for translating rotary movement of said disk into reciprocating movement of said heating element, a ratchet wheel, a spiral spring connected to said ratchet wheel and to said shaft, and means for actuating said wheel to wind said spring whereby energy is stored in said spring for moving said heating element.

5. In a refrigerator including a cooling unit upon which frost collects, a heating element spaced from the wall of said cooling unit, the heat radiating surface of said heating element being relatively smaller than said wall, said element Ibeing movably mounted for movement parallel to said Wall, and mechanism for reciprocating said heating element parallel to said wall for melting frost therefrom, said mechanism including a rotatable disk and a shaft therefor, a link engaging said disk near the outer periphery thereof and connected to said heating element for translating rotary movement of said disk into reciprocating movement of -said heating element, said shaft having a cam surface thereon, and a switch actuated by said cam surface for energizing said heating element.

6. In a refrigerator including a cooling unit upon which frost collects, a heating element spaced from the Wall of said cooling unit, the heat radiating surface of said heating element being relatively smaller than said wall, said element being movably mounted for movement parallel to said wall, and mechanism for reciprocating said heating element parallel to said wall for melting frost therefrom, said mechanism including a rotatable disk and a shaft therefor, a link engaging said disk near its outer periphery and connected to said heating element for translating rotary movement of said disk into reciprocating movement of said heating element, a ratchet wheel, a spiral spring connected to said ratchet wheel and to said shaft, means for actuating said wheel to wind said spring whereby energy is stored in said spring for moving said heating element, said shaft having a cam surface thereon, and a. switch actuated by said cam surface for energizing said heating element.

7. In a. refrigerator including a cooling unit upon which frost collects, a heating element spaced from the wall of said cooling unit, the heat radiating surface of said heating element `being relatively smaller than said wall, said element being movably mounted for movement parallel to said wall, and mechanism for reciprocating said heating element parallel to said wall for melting frost therefrom, said mechanism including a rotatable disk and a shaft therefor, a link engaging said disk near its outer periphery and connected to said heating element for translating rotary movement of said disk into reciprocating movement of said heating element, a ratchet wheel, a spiral spring connected to said ratchet wheel and to said shaft, and means for actuating said Wheel to wind said spring whereby energy is stored in said spring for moving said heating element, said shaft having a, cam surface thereon, said ratchet wheel including a hub having a cooperating cam surface thereon, a switch for energizing said heating element, and an arm actuated by axial movement of said ratchet wheel for actuating said switch, said cooperating cam surfaces being effective for causing axial movement of said ratchet wheel and actuation of said switch when frost on said cooling unit blocks said heating element and prevents rotation of said disk.

8. In a refrigerator including a cooling unit upon which frost collects, a heating element spaced from the walls of said cooling unit, the heat radiating surface of said heating element being relatively smaller than said walls, means for movably mounting said heating element for movement parallel to said walls, a rotatable rod extending transversely of said cooling unit, two arms secured to said rod, each of said arms extending adjacent a corresponding side wall of said cooling unit, said arms `being connected to said heating element, means including a rotatable disk for effecting reciprocation of said heating element, a pin mounted on said disk near the outer periphery thereof, one of said arms including a slot for receiving said pin whereby rotation of said disk is translated through said pin and slot connection into oscillation of said arm and reciprocation of said heating element for melting frost from said cooling unit.

LEONARD W. ATCHISON.

References Cited in the file of this patent UNITED STATES PATENTS 

